Synarel (Nafarelin) - Nasal

What Is Synarel?

Synarel (nafarelin) is a prescription nasal spray used to treat the symptoms of endometriosis in adults and central precocious puberty (early puberty) in children.

Synarel belongs to a group of medications called gonadotropin-releasing hormone (GnRH) agonists. GnRH agonists work by decreasing your body’s production of certain hormones, including estrogen and testosterone.

This medication is available as a nasal solution administered through a nasal spray.

Drug Facts

Generic Name: Nafarelin

Brand Name(s): Synarel

Drug Availability: Prescription

Administration Route: Nasal

Therapeutic Classification: 

Available Generically: No

Controlled Substance: N/A

Active Ingredient: Nafarelin

Dosage Form(s): Spray

What Is Synarel Used For?

The U.S. Food and Drug Administration (FDA) approved Synarel to treat:

  • Symptoms of endometriosis in adults
  • Central precocious puberty in children


The tissue that lines the inside of the uterus is called the endometrium. This tissue builds up during a regular menstrual cycle and is shed if you don’t become pregnant, resulting in your period.
People with endometriosis have endometrium growing outside their uterus. This tissue may be present on the ovaries, fallopian tubes, or other structures in the pelvis or abdomen.

Because this tissue responds to hormones just like the lining of your uterus, it will build up and bleed during your menstrual cycle, which can cause painful symptoms. Symptoms of endometriosis include severe menstrual cramps, pain during sex, low back pain, and painful bowel movements.

By decreasing estrogen levels, Synarel causes the tissue growth to shrink or disappear and helps improve your symptoms. Because Synarel can weaken your bones, you should not use Synarel for more than six months.

Central Precocious Puberty

Central precocious puberty, or CPP, is a condition that causes sexual development too early in children—before the age of 8 for girls and before 9 for boys.

Symptoms of CPP include:

  • Acne
  • A rapid increase in height (“growth spurt”) that stops suddenly at an early age
  • Breast development and menstruation in girls 
  • Facial hair, voice changes, and penis and testicle growth in boys 
  • Pubic and underarm hair growth 
  • Underarm body odor

Synarel helps stop puberty in children. If Synarel is tolerated, treatment should continue until puberty is desired.

How to Take Synarel

Synarel comes as a nasal spray. To be effective, Synarel must be used twice per day, every day, without missing a dose. When used to treat endometriosis, Synarel should be started two to four days after your period begins. Continue to take Synarel twice per day, every day. The usual treatment duration for endometriosis is six months. For CPP, treatment should be continued until puberty is desired.

Here are some tips for using Synarel:

  • Each new bottle of Synarel must be primed before your first dose. Follow the instructions that come with your prescription for priming—only prime new bottles of Synarel. Do not prime before each dose.
  • Clean the spray tip of your Synarel bottle before and after each use. This prevents the tip from becoming clogged, which could cause you to get the wrong dose. Follow the instructions provided with your prescription for cleaning steps. Do not use a pointed object to clean the tip. Do not take the bottle apart.
  • Before administering your dose, gently blow your nose to clear your nostrils. If you administer Synarel to a young child, you may need to use a bulb suctioner to clear their nose.
  • Follow the instructions provided with your prescription for administering your dose of Synarel. If your dose requires more than one pump into the same nostril (for CPP), wait at least 30 seconds before administering the next pump.
  • After administering your dose, tilt your head back for a few seconds to allow Synarel to spread over the back of your nose.
  • Do your best to avoid sneezing during or right after administering Synarel.
  • If you use a nasal decongestant spray, wait at least two hours after taking Synarel before using.


Synarel should be stored at room temperature (68 F to 77 F). Be sure to keep the bottle upright and protected from light. Do not freeze Synarel. Keep Synarel—and all your medications—in a safe location, up high and out of the reach of children and pets.

How Long Does Synarel Take to Work?

If you’re using Synarel to treat endometriosis, you may notice irregular vaginal spotting or bleeding during the first two months of therapy. After two months, your menstrual flow should become lighter or completely stop. Contact your healthcare provider if you still have regular periods after two months.

When Synarel is used for central precocious puberty, certain hormones increase during the first month. This can cause an increase in symptoms, including vaginal bleeding and breast enlargement in girls. Within one month, signs of puberty should begin to stop.

What Are the Side Effects of Synarel?

This is not a complete list of side effects, and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your pharmacist or a healthcare provider. You may report side effects to the FDA at or 800-FDA-1088.

Common Side Effects

Side effects are common with Synarel. Because Synarel decreases estrogen levels, side effects often resemble symptoms of menopause. People using Synarel to treat endometriosis may experience:

Children taking Synarel to treat CPP may develop:

  • Acne 
  • An increase in pubic hair (temporary)
  • Body odor 
  • Flaky, scaly skin
  • Hot flashes
  • Stuffy or runny nose
  • White or brown vaginal discharge

Be sure to let your healthcare provider know about any side effects that bother you or don’t go away.

Severe Side Effects

Rarely, Synarel may cause severe side effects. Call your healthcare provider immediately if you develop any serious reactions. Call 911 if your symptoms feel life-threatening. Serious side effects include the following:


Seizures have rarely occurred in people taking drugs similar to Synarel. Let your healthcare provider know if you:

Pituitary Apoplexy

Pituitary apoplexy (a very serious pituitary gland problem) has rarely occurred, often within two weeks of starting Synarel. Call your healthcare provider immediately if you experience:

  • A sudden headache
  • Eye weakness, an inability to move your eyes, or a change in eyesight 
  • Loss of consciousness 
  • Mood changes
  • Vomiting

Behavior or Mood Changes

Behavior or mood changes may occur in children. Contact your child’s healthcare provider if you notice any new or worsening symptoms, including:

  • Aggression 
  • Crying 
  • Depression 
  • Feeling angry or irritable 
  • Mood swings 
  • Restlessness

Allergic Reactions

Seek medical care if you think you are having an allergic reaction. Signs of an allergic reaction include:

  • Shortness of breath
  • Chest pain
  • Hives and itching
  • Rash
  • Swelling of the mouth, face, lips, tongue, or throat
  • Difficulty talking or swallowing

Weak Bones

Weak bones (osteoporosis) may occur in adults that use Synarel, which may not be reversible. For this reason, Synarel should not be used for longer than six months when used to treat endometriosis.

Ovarian Cysts

Ovarian cysts may occur within the first two months of treatment. Your risk of developing ovarian cysts is greater if you have polycystic ovarian syndrome (PCOS). Most ovarian cysts will go away on their own, but discontinuing Synarel or surgically removing the cysts is sometimes required.

Long-Term Side Effects

Synarel may cause your bones to weaken. In some cases, the effects may be irreversible. For this reason, Synarel should not be used for longer than six months to treat endometriosis.

You may be at increased risk of developing weak bones if you:

  • Drink excessive amounts of alcohol
  • Smoke
  • Have a family history of osteoporosis
  • Regularly take certain medications, such as anti-seizure medicines or steroids

Talk with your healthcare provider about your risk factors to determine if Synarel is appropriate.

Report Side Effects

Synarel may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your healthcare provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

Dosage: How Much Synarel Should I Take?

Drug Content Provided and Reviewed by IBM Micromedex®

The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For nasal dosage form (spray):
    • For treatment of central precocious puberty:
      • Children—Two sprays in each nostril 2 times a day, in the morning and in the evening. This provides a total dose of 8 sprays a day. Some patients may need a larger dose by using 3 sprays in alternating nostrils 3 times a day to provide a total of 9 sprays per day.
    • For treatment of endometriosis:
      • Adults—One spray into one nostril in the morning and one spray into the other nostril in the evening, taken for 6 months. Start your treatment between Days 2 and 4 of your menstrual period.
      • Children—Use and dose must be determined by your doctor.

Missed Dose

It is important not to miss any doses of Synarel. Even one missed dose can cause symptoms to return, including vaginal bleeding. Setting an alarm on your phone can be helpful.

If you miss a dose of Synarel, take it as soon as you remember. If it’s almost time for your next dose, skip the missed dose and resume your regular dosing schedule. Do not double up or take extra Synarel. If you miss two or more doses, call your healthcare provider.

Overdose: What Happens If I Take Too Much Synarel?

A Synarel overdose is not expected to cause any adverse reactions, but it’s important only to take your prescribed dose. If you’ve taken too much Synarel, call your healthcare provider or the Poison Control Center. If you develop symptoms that feel life-threatening, call 911.

If you think you or someone else may have overdosed on Synarel, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking Synarel, call 911 immediately.


Drug Content Provided and Reviewed by IBM Micromedex®

It is very important that your doctor check the progress of you or your child at regular visits to make sure that this medicine is working properly. Blood tests may be needed to check for unwanted effects. Be sure to keep all appointments.

For female patients: You should not use this medicine if you are pregnant or may become pregnant. Using this medicine while you are pregnant can harm your unborn baby. Use an effective form of birth control to keep from getting pregnant during treatment with this medicine. If you think you have become pregnant while using the medicine, tell your doctor right away.

For children using nafarelin spray for central precocious puberty (CPP): This medicine can cause a brief increase in blood levels of some hormones. During this time, you may notice more signs of puberty in your child, including light vaginal bleeding and breast enlargement in girls. If your child's symptoms do not improve within 4 weeks, or if they get worse, call your doctor.

For adult women using nafarelin spray for endometriosis:

  • For the first few days of treatment, the symptoms of your condition may get worse. This is normal. Do not stop using this medicine. Talk with your doctor if you have concerns about this.
  • During the time you are using nafarelin, your menstrual period may not be regular or you may not have a menstrual period at all. This is to be expected when being treated with this medicine. If regular menstruation does not begin within 2 to 3 months after you stop using this medicine, check with your doctor.
  • During the time you are using nafarelin spray, you should use birth control methods that do not contain hormones, such as condoms, IUD, a diaphragm or a cervical cap with a spermicide. If you have any questions about this, check with your doctor.
  • Use a water-based vaginal lubricant product if dryness of the vagina causes problems, such as pain during sexual intercourse. Make sure the lubricant you choose can be used with a latex birth control device if you are using one. Some lubricants contain oils, which can break down the latex rubber of condoms, a cervical cap, or a diaphragm, and cause them to rip or tear.
  • This medicine can cause your bone mineral density to decrease, which may lead to osteoporosis or weakened bones. Talk with your doctor about how this risk will affect you.
  • If you suspect you may have become pregnant, stop using this medicine and check with your doctor right away. There is a chance that continued use of nafarelin during pregnancy could cause birth defects or a miscarriage.

This medicine may cause some people to be agitated, irritable, or display other abnormal behaviors. Make sure the doctor knows if you have trouble sleeping, get upset easily, have a big increase in energy, or start to act reckless. Also tell the doctor if you have sudden or strong feelings, such as feeling nervous, angry, restless, violent, or scared. If you or your caregiver notice any of these side effects, tell your doctor right away.

Using this medicine may increase your risk of having seizures. Check with your doctor right away if you start to have muscle spasm or jerking of all extremities, seizures, sudden loss of consciousness, or loss of bladder control.

Nafarelin spray can increase your risk of having cysts in the ovaries. Talk to your doctor about this risk.

This medicine may cause intracranial hypertension or pseudotumor cerebri (increased pressure in the head) in children. Check with your doctor right away if your child have blurred or double vision, change in ability to see colors, especially blue or yellow, continuing ringing or buzzing or other unexplained noise in the ears, dizziness, eye pain, hearing loss, nausea and vomiting, or severe headache.

Before you have any medical tests, tell the medical doctor in charge that you are using this medicine. The results of some tests may be affected by this medicine.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

What Are Reasons I Shouldn’t Take Synarel?

Certain conditions increase your risk of developing complications from Synarel. Do not take Synarel if you:

  • Are pregnant or plan to become pregnant 
  • Are breastfeeding 
  • Have abnormal vaginal bleeding that a healthcare provider has not evaluated
  • Are allergic to nafarelin or any other ingredient in Synarel
  • Are allergic to Lupron (leuprolide) or Zoladex (goserelin)

What Other Medications Interact With Synarel?

Certain medications may interact with Synarel. Let your healthcare provider and pharmacist know about all your medications, including over-the-counter (OTC) nonprescription products and vitamins or herbal supplements.

Watch out for these common interactions:

  • Nasal decongestants: Nasal decongestant sprays can decrease how much Synarel is absorbed. If you need to use a nasal decongestant, wait at least two hours after taking Synarel. 
    Drugs that increase seizure risk: Some medications increase your chance of developing seizures from Synarel. Let your healthcare provider know if you take Wellbutrin (bupropion), selective serotonin reuptake inhibitors (SSRIs) like Prozac (fluoxetine), Paxil (paroxetine), or Lexapro (escitalopram), or any other antidepressant or antipsychotic medications

This is not a complete list of all the drugs that may interact with Synarel. Keep an up-to-date list of all your medicines and let your healthcare provider and pharmacist know of any changes.

What Medications Are Similar?

Synarel belongs to a group of medications called gonadotropin-releasing hormone (GnRH) agonists. Other GnRH agonists also used to treat endometriosis and central precocious puberty (CPP) include:

  • Lupron (leuprolide), which is used for endometriosis and CPP 
  • Zoladex (goserelin), which is used for endometriosis only

Unlike Synarel, both Lupron and Zoladex are injectable medications. These medications only need to be taken every one to six months, compared with Synarel’s daily dosing. However, Synarel may be a better option for those who are uncomfortable receiving injections.

This is a list of drugs also prescribed to treat endometriosis and CPP. It is NOT a list of drugs recommended to take with Synarel. In fact, you should not take these drugs together. Talk to your healthcare team about any questions or concerns about your treatment.

Frequently Asked Questions

  • What is Synarel used for?

    Synarel is used to treat the painful symptoms of endometriosis, including severe menstrual cramps, pain during sex, low back pain, and painful bowel movements. Synarel is also used in children to treat central precocious puberty (CPP), which causes puberty to start too early.

  • How does Synarel work?

    Synarel works by decreasing certain hormones in your body, including estrogen and testosterone. For people with endometriosis, low estrogen levels cause the endometrial tissue growing outside of the uterus to shrink or disappear, which helps improve symptoms. For children with CPP, decreasing levels of these hormones helps stop puberty.

  • How long does it take for Synarel to work?

    When used to treat endometriosis, Synarel should reduce menstrual flow or stop your periods altogether by two months. Children with central precocious puberty will begin to notice signs that puberty is stopping within one month.

  • What are the side effects of Synarel?

    The most common side effects of Synarel in adults include hot flashes, headaches, vaginal dryness, mood changes, decreased interest in sex, and acne. In children, Synarel may cause acne, body odor, flaky skin, hot flashes, a temporary increase in pubic hair, a stuffy or runny nose, and white or brown vaginal discharge.

  • Does Synarel prevent pregnancy?

    No, Synarel is not meant for use to prevent pregnancy. If you miss doses of Synarel, your ovaries may release an egg (ovulation), and you could become pregnant. Becoming pregnant while using Synarel can harm the fetus. You must use a non-hormonal form of birth control (e.g., condoms, IUD, diaphragm with contraceptive jelly) while taking Synarel. Do not take birth control pills.

How Can I Stay Healthy While Taking Synarel?

Synarel is an effective treatment option for endometriosis and central precocious puberty, but you must take it every day without missing a dose for it to work. With all the stressors of daily life, it can be hard to remember your dose or to pick up your refill on time. Follow these tips to ensure you don’t miss a single dose:

  • Keep track of your doses on a calendar. 
  • Use an alarm on your phone to remind you to take each dose. 
  • Talk with your healthcare provider about how often you’ll need to refill your Synarel. This will depend on your dose. Set up automatic refills at your pharmacy and set an alarm on your phone that reminds you to pick up your refill a day or two before you need it.

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and is not intended to replace medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Johns Hopkins Medicine. Endometriosis.

  3. MedlinePlus. Central precocious puberty.

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By Christina Varvatsis, PharmD
Christina Varvatsis is a hospital pharmacist and freelance medical writer. She is passionate about helping individuals make informed healthcare choices by understanding the benefits and risks of their treatment options.